The present invention relates to a liquid crystal type rear-projection television which, in particular, has a thinner cabinet.
FIGS. 1 and 2 show a conventional CRT-built-in-type rear-projection television 1. CRTs 3-5 of red (R), green (G) and blue (B) are incorporated in a cabinet 2. Light beams of the respective colors emitted from the respective CRTs 3-5 and carrying respective images are reflected by a mirror 6 that is obliquely disposed in the cabinet 2, and then the respective images are projected onto the rear surface of a screen 8 that is disposed at a front portion 7 of the cabinet 2, to form a color image on the front surface of the screen 8.
The rear-projection television 1 is usually placed in a house room or an office, and the cabinet 2, which is usually large, occupies a wide space of the room. The above configuration including the inclined mirror 6 is employed to reduce the depth (thickness) of the cabinet 2, to thereby save the room space.
Since the CRTs 3-5 are also large, they occupy a large part of the whole rear projection television 1. If the rear-projection television 1 has a diagonal size of 40 inches (600 mm vertically and 800 mm horizontally), the axial length B of the respective CRTs 3-5 is about 450 mm. Due to limitations from the magnification and peripheral performance of projection lenses, an optical path length C+D from each of the CRTs 3-5 to the screen 8 should be at least about 800 mm. Since the television 1 is for home use, the height of the cabinet 2 is designed to be about 1,100 mm. Therefore, in order to obtain the above length C+D, the thickness E of the cabinet 2 should be at least about 470 mm.
As long as designed according to the above conventional design concept, the cabinet thickness of 40-inch CRT-type rear-projection televisions cannot be made smaller than about 450 mm.
On the other hand, liquid crystal type rear-projection televisions have been proposed recently which employ a liquid crystal projector instead of CRTs. The liquid crystal projector includes three liquid crystal panels of R, G and B, and light beams carrying respective three images are output from a single projection lens. However, even in such liquid crystal type rear-projection televisions, the liquid crystal panels and the projection lens are disposed at the position of the center CRT 4 of the CRT-type projection television 1, and the light beams emitted from the liquid crystal projector are reflected by a mirror and made incident on a screen.
In the liquid crystal type rear-projection televisions having the single projection lens, although the cabinet thickness can be made smaller than the CRT-type projection televisions, there still exists a certain limit of the cabinet thickness that originates, for instance, from an increased projection length of the liquid crystal projector. Further, some problems remain unsolved in the convergence adjustment.